Stalk Borer Movement

Growing Degree Day (GDD) accumulations can help growers monitor stalk borer hatch and movement by using GDD accumulated with a developmental threshold of
41º F. Common stalk borer eggs typically begin to hatch at 575 GDDs. They wrap up first hatch and begin feeding on weeds and grasses at 750 GDDs. At 1,300 GDDs, the first 10 percent of caterpillars begin to move into the corn crop and scouting should begin. At 1,400 GDDs, 50 percent of the caterpillars will have moved into corn.

The chart offers stalk borer scouting recommendations.

Common Stalk Borer Caterpillar Activity Based on Accumulated Degree Days

Accum. Degree Days Common Stalk Borer Caterpillar Activity Recommendation
0-574 Conditions favorable for egg hatch. No scouting necessary.
575-749 Eggs begin to hatch. No scouting necessary.
750-1299 Young caterpillars begin boring into grass and weeds. No scouting necessary. Avoid spraying grass and weeds along field edges.
1300-1399 10% of caterpillars begin moving into adjacent corn. Begin scouting field edges for defoliation.
1400-1700 50% of caterpillars moving into adjacent corn. Continue scouting for defoliation along field edges. Spray if necessary.
Source: South Dakota State University.